Objective: To investigate whether reader training improves the performance and agreement of radiologists in interpreting unenhanced breast magnetic resonance imaging (MRI) scans using diffusion-weighted imaging (DWI). Materials and Methods:A study of 96 breasts (35 cancers, 24 benign, and 37 negative) in 48 asymptomatic women was performed between June 2019 and October 2020.High-resolution DWI with b-values of 0, 800, and 1200 sec/mm 2 was performed using a 3.0-T system.Sixteen breast radiologists independently reviewed the DWI, apparent diffusion coefficient maps, and T1-weighted MRI scans and recorded the Breast Imaging Reporting and Data System (BI-RADS) category for each breast.After a 2-h training session and a 5-month washout period, they re-evaluated the BI-RADS categories.A BI-RADS category of 4 (lesions with at least two suspicious criteria) or 5 (more than two suspicious criteria) was considered positive.The per-breast diagnostic performance of each reader was compared between the first and second reviews.Inter-reader agreement was evaluated using a multi-rater κ analysis and intraclass correlation coefficient (ICC).Results: Before training, the mean sensitivity, specificity, and accuracy of the 16 readers were 70.7% (95% confidence interval [CI]: 59.4-79.9),90.8% (95% CI: 85.6-94.2),and 83.5% (95% CI: 78.6-87.4),respectively.After training, significant improvements in specificity (95.2%; 95% CI: 90.8-97.5;P = 0.001) and accuracy (85.9%; 95% CI: 80.9-89.8;P = 0.01) were observed, but no difference in sensitivity (69.8%; 95% CI: 58.1-79.4;P = 0.58) was observed.Regarding inter-